This is basically what is called "tethering", using the 3G internet connection of the phone for other devices (such as your laptop), except that the "tether" is no a physical connection but just a wifi connection. In other words, you put your phone into this mode and you can connect to it through wifi and have wireless internet anywhere you have 3G coverage. AT&T does not offer the same service.
Of course, it's worth noting that tethering isn't a "service" that carriers have to build or support. It's an inherent capability of a sufficiently advanced computing device that has access to two networks simultaneously. But in a textbook case of non-neutrality, AT&T (and others) prevent you from using that capability unless you pay them to remove the entirely artificial restriction.
Quite so. AT&T restricts your ability to tether, because there are still unlimited data plans and they don't want people to fully take advantage of those plans.
